U.S. patent number 9,453,784 [Application Number 14/017,386] was granted by the patent office on 2016-09-27 for non-intrusive measurement of hot gas temperature in a gas turbine engine.
This patent grant is currently assigned to SIEMENS ENERGY, INC.. The grantee listed for this patent is Siemens Energy, Inc.. Invention is credited to Heiko Claussen, Upul P. DeSilva, Justinian Rosca, Nancy H. Ulerich, Michelle Xiaohong Yan.
United States Patent |
9,453,784 |
DeSilva , et al. |
September 27, 2016 |
Non-intrusive measurement of hot gas temperature in a gas turbine
engine
Abstract
A method and apparatus for operating a gas turbine engine
including determining a temperature of a working gas at a
predetermined axial location within the engine. An acoustic signal
is encoded with a distinct signature defined by a set of
predetermined frequencies transmitted as a non-broadband signal.
Acoustic signals are transmitted from an acoustic transmitter
located at a predetermined axial location along the flow path of
the gas turbine engine. A received signal is compared to one or
more transmitted signals to identify a similarity of the received
signal to a transmitted signal to identify a transmission time for
the received signal. A time-of-flight is determined for the signal
and the time-of-flight for the signal is processed to determine a
temperature in a region of the predetermined axial location.
Inventors: |
DeSilva; Upul P. (Oviedo,
FL), Claussen; Heiko (Plainsboro, NJ), Yan; Michelle
Xiaohong (Princeton, NJ), Rosca; Justinian (West
Windsor, NJ), Ulerich; Nancy H. (Longwood, FL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Siemens Energy, Inc. |
Orlando |
FL |
US |
|
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Assignee: |
SIEMENS ENERGY, INC. (Orlando,
FL)
|
Family
ID: |
51398960 |
Appl.
No.: |
14/017,386 |
Filed: |
September 4, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150063411 A1 |
Mar 5, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02C
7/32 (20130101); G01H 3/00 (20130101); G01K
11/24 (20130101); G01K 13/02 (20130101); G01M
15/14 (20130101); G01K 13/024 (20210101); F05D
2260/83 (20130101) |
Current International
Class: |
G01K
11/24 (20060101); G01M 15/14 (20060101); G01H
3/00 (20060101); G01K 13/02 (20060101); F02C
7/32 (20060101) |
Field of
Search: |
;374/119 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0304170 |
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Feb 1989 |
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EP |
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2004108826 |
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Apr 2004 |
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JP |
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Other References
Roberto Roubicek; Gas Temperature Measurement in the Fireside of
Process Heaters-Using Acoustic Pyrometry; 2003 NPRA Maintenance
Conference; 2003; Salt Lake City, Utah. cited by applicant .
J. A. Kleppe et al.; The Application of Acoustic Pyrometry to Gas
Turbines and Jet Engines; AIAA 98-3611; 1998. cited by applicant
.
Gustave C. Fralick et al.; Passive Acoustic Tomography Tested for
Measuring Gas Temperatures; Research and Technology 2003; May 2004;
NASA Glenn Research Center, Cleveland, OH. cited by applicant .
Gustave C. Fralick; Acoustic Pyrometry Applied to Gas Turbines and
Jet Engines; www.grc.nas.gov/WWW/RT/RT1998/5000/5510; 1998. cited
by applicant .
Dr. Peter Ariessohn; Development of an Acoustic Sensor for On-Line
Gas Temperature Measurement in Gasifiers; Technical Progress
Report; Enertechnix, Inc.; Quarterly Report Oct. 1, 2005 to Dec.
31, 2005; Issued Jan. 15, 2006; 12 pages. cited by applicant .
Brian Moss et al.; Temperature Measurement of Gases using Acoustic
Means; 2009 6th International Multi-Conference on Systems, Signals
and Devices; 2009; 6 pages. cited by applicant .
Raviraj Adve; University of Toronto; "Smart Antennas" course notes;
2007; 25 pages. cited by applicant .
Dr. Peter Ariessohn; Development of an Acoustic Sensor for On-Line
Gas Temperature Measurement in Gasifiers; Final Report;
Enertechnix, Inc.; Final Report Jun. 11, 2003-Jun. 20, 2008; Issued
Jul. 31, 2008; 57 pages. cited by applicant .
Mauro Bramanti et al.; An Acoustic Pyrometer System for Tomographic
Thermal Imaging in Power Plant Boilers; IEEE Transactions on
Instrumentation and Measurement; vol. 45, No. 1; Feb. 1996; 9
pages. cited by applicant .
G.Q. Shen et al.; Real-Time Monitoring on Boiler Combustion Based
on Acoustic Measurement; IEEE Power India Conference; 2006; 4
pages. cited by applicant .
R.H. Stones et al.; The Application of Acoustic Pyrometry to Gas
Temperature Measurement and Mapping; IEEE Colloquium on Ultrasound
in the Process Industry; Sep. 23, 1993; 2 pages. cited by applicant
.
John A. Kleppe et al.; The Application of Digital Signal Processing
to Acoustic Pyrometry; Proc. 1996 IEEE Digital Signal Processing
Workshop; 1996; pp. 420-422. cited by applicant .
John A. Kleppe et al.; The Application of Image Processing to
Acoustic Pyrometry; 1996; pp. 657-659. cited by applicant .
K. Srinivasan et al.; Effects of acoustic source and filtering on
time-of-flight measurements; Applied Acoustics 70; 2009; pp.
1061-1072. cited by applicant .
William J. Norris et al.; The Measurement of Performance of
Combustors Using Passive Acoustic Methods: Additional Results; 43rd
AIAA Aerospace Sciences Meeting and Exhibit; Jan. 10-13, 2005;
American Institute of Aeronautics and Astronautics; 9 pages. cited
by applicant .
TMS 2000--Theory of Operation; SEI, Inc.; Mar. 1, 2002; 2 pages.
cited by applicant .
Upul Desilva et al.; Novel Gas Turbine Exhaust Temperature
Measurement System; Proceedings of the ASME Turbo Expo 2013;
GT2013-95153; Jun. 3-7, 2013; 8 pages. cited by applicant.
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Primary Examiner: Phan; Minh
Assistant Examiner: Rhodes, Jr.; Leon W
Government Interests
STATEMENT REGARDING FEDERALLY SPONSORED DEVELOPMENT
Development for this invention was supported in part by Contract
No. DE-FC26-05NT42644, awarded by the United States Department of
Energy. Accordingly, the United States Government may have certain
rights in this invention
Claims
What is claimed is:
1. A method of operating a gas turbine engine, including
determining a temperature of a working gas passing through a flow
path within the gas turbine engine, the method comprising the steps
of: transmitting an acoustic signal from an acoustic transmitter
located at a predetermined axial location along the flow path of
the gas turbine engine; receiving the acoustic signal from the
acoustic transmitter at an acoustic receiver located at the
predetermined axial location; the acoustic signal being encoded
with a distinct signature defined by a set of predetermined
frequencies transmitted as a non-broadband acoustic signal; wherein
receiving the acoustic signal includes comparing a received signal
to one or more transmitted signals to identify a similarity of the
received signal to a transmitted signal to identify a transmission
time for the received signal; determining a time-of-flight for the
signal from the acoustic transmitter to the acoustic receiver; and
processing the time-of-flight for the signal to determine a
temperature in a region of the predetermined axial location.
2. The method of claim 1, wherein comparing the received signal to
one or more transmitted signals includes correlating frequencies of
the received signal to a distinct signature of a transmitted signal
to identify a transmission time for the signal.
3. The method of claim 1, wherein the set of predetermined
frequencies transmitted as a distinct signature comprises a set of
frequencies transmitted simultaneously for a predetermined time
duration.
4. The method of claim 3, wherein each of the frequencies of the
distinct signature has an associated preset amplitude, and
receiving the signal includes verifying a predetermined amplitude
level for a plurality of the frequencies in the distinct signature
received at the receiver to identify the corresponding distinct
signature and an associated transmission time for the signal.
5. The method of claim 1, including a plurality of distinct
signatures, where each of the distinct signatures have a different
set of predetermined frequencies than at least one other of the
distinct signatures.
6. The method of claim 5, wherein the plurality of distinct
signatures are transmitted simultaneously from a plurality of
respective transmitters located around the flow path at the
predetermined axial location.
7. The method of claim 6, wherein the plurality of distinct
signatures are uncorrelated to each other.
8. The method of claim 1, including transmitting a series of the
distinct signatures sequentially in time, each of the distinct
signatures having the same set of predetermined frequencies.
9. The method of claim 1, wherein transmission of each acoustic
signal includes continuously generating the acoustic signal at a
signal generator and operating an audio switch between the signal
generator and the transmitter to selectively transmit portions of
the continuously generated signal from the transmitter.
10. The method of claim 1, including monitoring a current
background noise within the gas path on-line and adjusting the set
of predetermined frequencies forming one or more distinct
signatures to have a low correlation to the current background
noise.
11. A gas turbine engine including an apparatus for controlling
operation of the gas turbine engine, and the engine having a
boundary structure defining a flow path passing through the engine,
the apparatus for controlling operation of the engine comprising:
at least one acoustic transmitter located on the boundary structure
at a predetermined axial location along the flow path; at least one
acoustic receiver located on the boundary structure at the
predetermined axial location; a signal generator producing at least
one signal having a distinct signature defined by a set of
predetermined frequencies forming a non-broadband signal; a signal
processor configured to compare signals received at the receiver to
one or more transmitted signals to identify a similarity of a
received signal to a transmitted signal to identify a transmission
time for the received signal, and the processor configured to
determine a time-of-flight for the received signal and to process
the time-of-flight to determine a temperature in a region of the
predetermined axial location.
12. The apparatus of claim 11, including a signal generator for
connection to the transmitter that continuously produces the at
least one signal for a plurality of time-of-flight
measurements.
13. The apparatus of claim 12, including an audio switch between
the signal generator and the transmitter to provide a signal to the
transmitter from the generator for predetermined durations at
predetermined spaced time intervals.
14. The apparatus of claim 11, including a plurality of acoustic
transmitters and receivers located around a circumference of the
boundary structure.
15. The apparatus of claim 11, including a plurality of signal
generators connected to respective ones of the signal generators to
provide a unique signal, having a distinct signature, to each of
the transmitters.
16. The apparatus of claim 15, wherein the signal generators
continuously produce the signals provided to the transmitters, and
including an audio switch between each of the signal generators and
the transmitters to provide a signal to each transmitter from a
respective generator for predetermined durations at predetermined
spaced time intervals.
Description
FIELD OF THE INVENTION
The present invention relates to temperature measurement in turbine
engines and, more particularly, to determination of temperature of
a hot gas using acoustic measurements in a gas turbine engine.
BACKGROUND OF THE INVENTION
Combustion turbines, such as gas turbine engines, generally
comprise a compressor section, a combustor section, a turbine
section and an exhaust section. In operation, the compressor
section can induct and compress ambient air. The combustor section
generally may include a plurality of combustors for receiving the
compressed air and mixing it with fuel to form a fuel/air mixture.
The fuel/air mixture is combusted by each of the combustors to form
a hot working gas that may be routed to the turbine section where
it is expanded through alternating rows of stationary airfoils and
rotating airfoils and used to generate power that can drive a
rotor. The expanding gas exiting the turbine section can be
exhausted from the engine via the exhaust section.
The fuel/air mixture at the individual combustors is controlled
during operation of the engine to maintain one or more operating
characteristics within a predetermined range, such as, for example,
to maintain a desired efficiency and/or power output, control
pollutant levels, prevent pressure oscillations and prevent
flameouts. In a known type of control arrangement, a bulk turbine
exhaust temperature may also be monitored as a parameter indicative
of a condition in the combustor section. For example, a controller
may monitor a measured turbine exhaust temperature relative to a
reference temperature value, and a measured change in temperature
may result in the controller changing the fuel/air ratio at the
combustor section.
In a known temperature monitoring system for controlling combustion
operations, temperature monitors, such as thermocouples, are
located directly in the exhaust flow of the turbine. Such
monitoring systems generally require locating thermocouples at
different fixed axial locations along the exhaust flow, which may
introduce uncertainties in relation to temperature calculations for
controlling the engine as conditions affecting operation of the
engine change, such as a varying load condition on the engine.
Providing temperature measurements of the hot working gas upstream
of the turbine section has proven problematic due to difficulties
in providing a sensor system capable of providing accurate
temperature measurements on a long term basis in this region of the
engine.
SUMMARY OF THE INVENTION
In accordance with an aspect of the invention, a method of
operating a gas turbine engine is provided, including determining a
temperature of a working gas passing through a flow path within the
gas turbine engine. The method comprises the steps of transmitting
an acoustic signal from an acoustic transmitter located at a
predetermined axial location along the flow path of the gas turbine
engine. The acoustic signal is received from the acoustic
transmitter at an acoustic receiver located at the predetermined
axial location, the acoustic signal being encoded with a distinct
signature defined by a set of predetermined frequencies transmitted
as a non-broadband acoustic signal. The step of receiving the
acoustic signal includes comparing a received signal to one or more
transmitted signals to identify a similarity of the received signal
to a transmitted signal to identify a transmission time for the
received signal. A time-of-flight is determined for the signal from
the acoustic transmitter to the acoustic receiver, and the
time-of-flight for the signal is processed to determine a
temperature in a region of the predetermined axial location.
The step of comparing the received signal to one or more
transmitted signals may include correlating frequencies of the
received signal to a distinct signature of a transmitted signal to
identify a transmission time for the signal.
The set of predetermined frequencies transmitted as a distinct
signature may comprise a set of frequencies transmitted
simultaneously for a predetermined time duration.
Each of the frequencies of the distinct signature may have an
associated preset amplitude, and receiving the signal may include
verifying a predetermined amplitude level for a plurality of the
frequencies in the distinct signature received at the receiver to
identify the corresponding distinct signature and an associated
transmission time for the signal.
A plurality of distinct signatures may be provided, where each of
the distinct signatures have a different set of predetermined
frequencies than at least one other of the distinct signatures.
The plurality of distinct signatures may be transmitted
simultaneously from a plurality of respective transmitters located
around the flow path at the predetermined axial location.
The plurality of distinct signatures may be uncorrelated to each
other.
A series of the distinct signatures may be transmitted sequentially
in time, each of the distinct signatures having the same set of
predetermined frequencies.
Transmission of each acoustic signal may include continuously
generating the acoustic signal at a signal generator and operating
an audio switch between the signal generator and the transmitter to
selectively transmit portions of the continuously generated signal
from the transmitter.
A current background noise may be monitored within the gas path
on-line and the set of predetermined frequencies may be adjusted
forming one or more distinct signatures to have a low correlation
to the current background noise.
In accordance with another aspect of the invention, a gas turbine
engine is provided including an apparatus for controlling operation
of the gas turbine engine, and the engine having a boundary
structure defining a flow path passing through the engine. The
apparatus for controlling operation of the engine comprises at
least one acoustic transmitter located on the boundary structure at
a predetermined axial location along the flow path, and at least
one acoustic receiver located on the boundary structure at the
predetermined axial location. A signal generator that produces at
least one signal having a distinct signature defined by a set of
predetermined frequencies forming a non-broadband signal. A signal
processor is configured to compare signals received at the receiver
to one or more transmitted signals to identify a similarity of a
received signal to a transmitted signal to identify a transmission
time for the received signal. The processor is configured to
determine a time-of-flight for the received signal and to process
the time-of-flight to determine a temperature in a region of the
predetermined axial location.
A signal generator may be provided for connection to the
transmitter that continuously produces the at least one signal for
a plurality of time-of-flight measurements.
An audio switch may be located between the signal generator and the
transmitter to provide a signal to the transmitter from the
generator for predetermined durations at predetermined spaced time
intervals.
A plurality of acoustic transmitters and receivers may be located
around a circumference of the boundary structure.
A plurality of signal generators may be connected to respective
ones of the signal generators to provide a unique signal, having a
distinct signature, to each of the transmitters. The plurality of
signal generators may continuously produce the signals provided to
the transmitters, and an audio switch may be located between each
of the signal generators and the transmitters to provide a signal
to each transmitter from a respective generator for predetermined
durations at predetermined spaced time intervals.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing
out and distinctly claiming the present invention, it is believed
that the present invention will be better understood from the
following description in conjunction with the accompanying Drawing
Figures, in which like reference numerals identify like elements,
and wherein:
FIG. 1 is a perspective cross-sectional view of a gas turbine
engine illustrating implementation an acoustic temperature
measurement system in accordance with aspects of the present
invention;
FIG. 2 is a diagrammatic view of the system for determining
temperature;
FIG. 3A is a chart illustrating an encoded signal produced by
signal generator for transmission from a transducer in accordance
with an aspect of the invention;
FIG. 3B is a chart illustrating an encoded signal received by a
transducer and corresponding to the transmitted signal of FIG.
3A;
FIG. 4 is a schematic illustrating an apparatus including a
controller for providing a temperature determination in accordance
with aspects of the invention;
FIG. 5 is a schematic illustrating details of an audio switch in
accordance with aspects of the invention; and
FIG. 6 is a schematic illustrating an alternative configuration for
an audio switch in accordance with aspects of the invention.
DETAILED DESCRIPTION OF THE INVENTION
In the following detailed description of the preferred embodiment,
reference is made to the accompanying drawings that form a part
hereof, and in which is shown by way of illustration, and not by
way of limitation, a specific preferred embodiment in which the
invention may be practiced. It is to be understood that other
embodiments may be utilized and that changes may be made without
departing from the spirit and scope of the present invention.
A temperature measurement apparatus or system is described herein
that is configured to be used to continuously monitor high
temperature combustion gases, such as may be on the order of
1500.degree. F., as part of an on-line monitoring and control
system to be used on a long term basis within a gas turbine engine.
In accordance with an aspect of the invention, it has been noted
that acoustic pyrometry methods may be implemented to avoid placing
temperature probes directly within the hot combustion gas flow,
however, background noise associated with combustion, or other
engine generated noises, can hinder accurate detection of sound
signals that are transmitted into and received from the combustion
gas path. The temperature measurement method and apparatus
described herein is directed to production of one or more unique
sound signals that are distinct and recognizable from sounds or
noises produced by the engine, enabling accurate association of a
received acoustic signal with a transmitted signal to enable
identification of the received signal as having been transmitted by
the system and to provide an associated time of transmission for
the received signal. Having identifiable signals, with associated
transmission and reception times, provides data for time-of-flight
calculations of the signals through the hot gas path which can be
used to estimate the temperature of locations within the gas
path.
Referring to FIG. 1, embodiments of the invention are directed to
an acoustic temperature measurement system 24 that may be
incorporated in a gas turbine engine 10 and to methods of using the
acoustic temperature measurement system 24 to determine
temperatures at predetermined locations in the engine 10 and to
control an operation of the engine 10. Aspects of the invention
will be explained in connection with possible configurations of the
system 24, but the detailed description is intended only as
exemplary.
Referring to the drawings, and in particular to FIG. 1, a portion
of an exemplary gas turbine engine 10 is shown. The exemplary
engine 10 includes a compressor section 12, a combustor section 14,
a turbine section 18, and an exhaust section 20. The combustor
section 14 includes a plurality of combustor baskets or combustors
16 and associated transition ducts 22, wherein the combustors 16
and transition ducts 22 define a flow path or passage 17 for
conveying a hot working gas to the turbine section 18.
During operation of the engine 10, compressed air from the
compressor section 12 is provided to the combustor section 14 where
it is combined with fuel in the combustors 16, and the fuel/air
mixture is ignited to form combustion products comprising the hot
working gas. It may be understood that combustion of the fuel and
air may occur at various axial locations along the passage to the
inlet 18a of the turbine section 18. The hot working gas is
expanded through the turbine section 18 and is exhausted through
the exhaust section 20.
The acoustic temperature measurement system 24, is described herein
with reference to locating acoustic devices
(transmitters/receivers) for the system 24 at or adjacent to the
inlet 18a for the turbine section 18 for determining a turbine
inlet temperature, however, it may be understood that the system
24, and methods of operation for the system 24 may be implemented
at other locations along the engine 12, such as at the exhaust
section 20. In the described embodiment, the acoustic devices for
the system 24 are positioned on the transition ducts 22 and a
plurality of the acoustic devices may be located in a measurement
plane of each transition duct 22 extending generally perpendicular
to a longitudinal axis of the respective transition duct 22, i.e.,
perpendicular to a flow path 17 of the hot working gas within the
duct 22. The location of the measurement plane defines a
predetermined axial location at which temperature measurements are
obtained along the flow path of the gas turbine engine 12.
A diagrammatic view of the acoustic temperature measurement system
24 is illustrated in FIG. 2, taken at a cross-section of one of the
transition ducts 22. The system 24 comprises a plurality of audio
transducer units 40 (only one transducer 40 shown in FIG. 1)
supported around the circumference of the transition duct 22. The
transducer units 40 are illustrated in FIG. 2 diagrammatically by
the eight transducer units labeled 40A-40H, and may each include a
housing supporting a speaker (transmitter) 42 and a microphone
(receiver) 44, as indicated on transducer unit 40A. It should be
understood that, within the spirit and scope of the present
invention, a greater number or fewer transducer units 40 may be
provided to perform a temperature sensing operation. For example,
it may be desirable to provide a greater number of transducer units
40 to provide greater accuracy in mapping of temperatures within
the flow path 17, as is described in greater detail below.
Each of the transducer units 40 includes an inner end that is
positioned at an opening in the transition duct 22, where the
transducer unit 40 is mounted to an outer surface of the transition
duct 22, to emit acoustic signals and to receive acoustic signals.
The transducer units 40 are connected to a processor or controller
46 that is configured to control the transducer units 40 to produce
predetermined output signals and to receive time-of-flight signals
corresponding to the output signals. The controller 46 is further
configured to store and process data corresponding to the received
signals to calculate temperatures and to produce outputs in
accordance with the calculated temperatures associated with the
received signals, as is described in greater detail below. The
controller 46 is additionally configured to provide control signals
for controlling operations affecting combustion, including signals
to the individual combustors 16, providing control of, for example,
the fuel/air ratio at the combustors 16.
During a data acquisition operation, at least one of the transducer
units 40 may comprise a transmitting unit 40 producing a signal
that traverses the hot gas flow path 17 in the plane defined by the
plurality of transducer units 40, and at least one of the
transducer units 40 may comprise a receiving unit 40, which is a
different transducer unit 40 than the transmitting transducer unit
40. The time-of-flight of a signal traveling between the
transmitting and the receiving units 40 may be used to determine an
average temperature of the gas through which the signal has
traveled. Specifically, the present invention uses the principle
that the speed of sound in a gas changes as a function of
temperature. For a determined or known composition of the gas, it
is possible to determine the temperature of the gas based on the
measured time for an acoustic or sound signal to travel the
distance between the transmitting and receiving transducers 40,
i.e., based on the speed of the sound signal traveling through the
gas. The temperature, T (.degree. C.), of the gas may be calculated
using the equation:
##EQU00001##
where: B=acoustic constant=
##EQU00002## (m/s) .gamma.=ratio of specific heats of the gas
R=universal gas constant, 8.314 J/mole- .degree.K M=molecular
weight of the gas (Kg/mole) d=distance traveled by sound signal (m)
t=time-of-flight of the sound signal (s)
Referring to FIG. 2, line-of-sound paths extending from two of the
transducer units 40A and 40D to each of the other transducer units
40 are shown to illustrate exemplary intersecting
line-of-sound-paths in accordance with an operation of the present
invention, it being understood that the line-of-sound paths from
each of the other transducer units 40 are formed in a similar
manner, but are not illustrated in FIG. 2. A transmitted signal
from each of the transducer units 40 may travel to and be received
at each of the other transducer units 40.
It should be understood that, in addition to any signals
transmitted from the transducer units 40, there is a substantial
amount of noise present within the transition duct 22, such as may
be produced by combustion events within and downstream from the
combustor 16. This noise is present at various frequencies,
including frequencies that may overlap frequencies of the acoustic
signals produced by the transducer units 40, and may make it
difficult to verify that received acoustic signals are valid
signals to be included in the processing of the data received for
performing a temperature determination. In accordance with an
aspect of the invention, signals generated by the system 24 are
formed as designed signals that can be clearly distinguished from
the noise that is generated by the engine. The designed signals are
formed with a predetermined signal pattern that is sparse in the
time-frequency domain is therefore likely to be uncorrelated to the
noise generated by the engine, which facilitates the ability to
recognize and separate the signal from the engine generated noise.
Also, the sparse signal pattern is designed to have a very narrow
autocorrelation, which helps in determining an accurate
time-of-flight in the presence of noise.
An example of a designed signal provided for transmission from a
transducer unit 40 is illustrated in FIG. 3A, and an example of a
corresponding signal received at another transducer unit 40 is
illustrated in FIG. 3B. As can be seen in FIGS. 3A and 3B, the
designed signals are depicted as distinct frequency marks,
generally designated 50, that are spaced in both frequency, i.e.,
non-broadband, and time. That is, a group of distinct frequencies,
e.g., four or five frequencies, are transmitted as a signal
sub-group at a particular time, and the signal sub-groups are
transmitted sequentially in time to form the encoded signal.
As illustrated in FIG. 3A, each signal sub-group is designated as
52.sub.n, where n=1, 2, 3 . . . , and the frequency marks 50 for
each signal group, depicting distinct frequencies, are designated
as 52.sub.nm, where m=a, b, c, . . . , as is particularly
illustrated for a first signal sub-group 52.sub.1. The
corresponding received signal depicted in FIG. 3B has similarly
labeled signal sub-groups that are designated as sub-groups
54.sub.n including distinct frequencies 54.sub.nm, as is
particularly illustrated for a first received signal sub-group
54.sub.1. As can be seen in FIG. 3A, each successive signal
sub-group 52.sub.n includes different distinct frequencies
52.sub.nm from the other signal sub-groups 52.sub.n forming the
transmitted signal.
Hence, in addition to the signal sub-groups 52.sub.n each forming a
distinct identifiable pattern, or individual signature, along the
frequency axis, i.e., sparsely correlated in the frequency domain,
the series of successive signal sub-groups 52.sub.n also form a
distinct identifiable pattern, or overall signature, of frequencies
along the time axis, i.e., sparsely correlated in the time domain.
That is, while a signature of the signal could be formed by only
one signal sub-group 52.sub.n defined by distinct frequencies,
forming a signature of a plurality of the subgroups 52.sub.n
increases the distinctness of the signature and forms a signal with
a sparse autocorrelation characteristic.
Further, it should be understood that in accordance with aspects of
the invention, the background noise received at the transducer
units 40 may be monitored by the system 24. Based on the detected
background noise, the system 24 may change the signature of the
transmitted signals in order to reduce the level of correlation
relative to the frequencies generated by the engine and present as
noise that is received at the transducer units 40.
The received signal sub-groups 54.sub.n arrive at the receiving
transducer 40 at some time after transmission from the transmitting
transducer 40, where the delay corresponds to the time-of-flight to
travel through the hot working gas, and may be used to determine
the gas temperature as described above. Further, the distinct
frequencies 52.sub.nm forming each signal sub-group 52.sub.n are
transmitted for a time duration that is longer than the time for
the signal sub-group to travel between the transmitting and
receiving transducers 40 in order to provide a substantial received
signal having a duration sufficiently long to be processed and
identified by frequency and amplitude. It may be understood that a
time-of-flight may be calculated for each signal sub-group based on
the time that the transmission of the transmitted signal sub-group
52.sub.n is initiated and the time that the received signal
sub-group 54.sub.n is initially received, i.e., based on the
leading edges of the signal sub-groups 52.sub.n, 54.sub.n. Hence,
the correlation of the received signal to the encoded transmitted
signal provides a verifiable time of transmission for use with the
detected reception time to determine an accurate
time-of-flight.
Referring to FIG. 4, the processor or controller 46 for performing
signal generation and signal processing is illustrated. The
controller 46 may include a signal generator 60 for producing a
signal encoded with a distinct signature, as described above with
reference to FIG. 3A. The signal generator 60 may operate under
control of a turbine control system 78, and preferably produces the
signal continuously, and an audio switch 62 controls output of the
signal from the signal generator 60 to the speaker in a source
transducer unit, designated 40.sub.S. The audio switch 62 is
selectively controlled (on/off) in the controller 46 to pass the
signal to the source transducer unit 40.sub.S. By using the audio
switch 62, the signal provided to the source transducer unit
40.sub.S will not include distortions of the signal, such as an
initial gradual signal ramp up or a gradual ending ramp down, that
could occur if the signal output were selectively controlled at the
signal generator 60. Rather, a sharp ramp at the beginning and end
of the signal, produced by turning the audio switch 62 on and off,
further enables formation of a distinct signal. Additionally, the
audio switch 62 can be used
The controller 46 further may include a datalogger 64 for receiving
and storing signals that are received at a receiver transducer unit
40.sub.R located across the flow path 17 from the source transducer
unit 40.sub.S. The datalogger 64 provides the signals to a noise
filter 66 where the received signals are compared to the encoded
signals that were sent from the source transducer unit 40.sub.S.
The filtering may be characterized as identifying received signals,
such as are illustrated in FIG. 3B, to the signals provided to the
source transducer unit 40.sub.S, as illustrated in FIG. 3A. The
received signals have distinct characteristics that include unique
groups of frequencies occurring at particular times and in a
particular sequence in time, and may additionally include a
distinct intensity or amplitude associated with each frequency.
Hence, each of these distinct characteristics may be used by the
noise filter 66 to filter out or identify the signals received by
the receiver transducer unit 40.sub.R that correspond to the
transmitted encoded signals. Other filtering techniques, such as
conventional filtering techniques, could also be employed to
additionally filter the received signals from noise.
Although the received signal may exhibit some distortion in
frequency and amplitude as a result of passing through the hot
working gas in the flow path 17, as seen from a comparison of the
signals in FIGS. 3A and 3B, the received frequencies will
substantially match the transmitted frequencies, and the amplitudes
of the received frequencies will be at or above a predetermined
amplitude level for a plurality of the frequencies in the distinct
signature received at the receiver transducer unit 40.sub.R. It may
be noted that there will be different attenuations of the
amplitudes for the different frequencies, and the attenuations at
the different frequencies will typically be constant for a given
system setup or environment in which the temperature measurement
system 24 is used. In FIGS. 3A and 3B, the different intensities or
amplitudes are illustrated by different shade lines on the
frequency marks 50 in these figures.
Filtered signals from the noise filter 66 are provided to a
time-of-flight estimator 68. The time-of-flight estimator 68
identifies valid time-of-flight data for providing a temperature
determination or estimate, and includes input from a physical
constraints and models module 70. In particular, the physical
constraints and models module 70 ensures that the time-of-flight
estimates fit within a predicted or modeled criteria for the
estimates. The physical constraints and models module 70 may
reference various physical parameters that may have an effect on
time-of-flight for the received signals including, for example, the
physical locations of the source and receiver transducer units
40.sub.S, 40.sub.R, physically achievable temperature ranges
including monitoring previously measured temperature maps, the
range of possible gas constants/properties, the range of possible
in plane flow and the resulting scattering of the time-of-flight,
the model for the propagation of the sound, the sensitivity of the
source and receiver transducer units 40.sub.S, 40.sub.R and the
maximal pressure levels for linear operation, and boundary
conditions such as those associated with the temperature of the
metal surfaces forming the boundary of the flow path 17.
The time-of-flight determinations or estimates are provided from
the time-of-flight estimator 68 to a temperature map estimator 72
which correlates multiple time-of-flight estimates to determine or
estimate a two-dimensional temperature map across the flow path 17,
based on the plurality of line-of-sound paths illustrated in FIG.
2. The temperature map estimator 72 operates in conjunction with a
temperature map models module 74 which provides a set of possible
temperature maps, such as previously recorded maps and/or their
basis functions. In particular, the temperature map will be a
linear combination of the basis functions for modeling the
temperatures within the area of flow path 17 at the measurement
plane defined by the transducers 40. The temperature maps may be
successive modifications of previous temperature maps, where each
successive temperature map may comprise a temperature map that
exhibits the least deviation from the measured time-of-flight
data.
The temperature map estimated at the temperature map estimator 72
is transferred to a temperature estimator at burners module 76 that
performs a back calculation to estimate the temperature at an
upstream location of a burner 22 for the combustor 16. The
estimated burner temperature is provided to the turbine control
system 78 for controlling the engine, such as for controlling the
fuel/air ratio at the burner 22. Additionally, the temperature may
be provided as an output 80, such as may be located at an operator
interface, for monitoring the engine.
Referring to FIG. 5, details of an audio switch 62 are illustrated
for switching a signal from the signal generator 60 to form
sequentially transmitted signals from each of the transducer units
40. In the present illustration, the audio switch 62 is configured
to sequentially switch signals to eight transducer units 40A-40H,
such as is shown in FIG. 2, where the audio switch 62 connects the
signal generator 60 to only one of the transducer units 40A-40H at
a time.
The audio switch 62 is diagrammatically depicted as including eight
signal gates G1-G8 with associated outputs S1-S8 , wherein only the
first and eighth gates G1 and G8 are illustrated, it being
understood that gates G2-G7 may be provided in the same manner as
is illustrated for G1 and G8. Each of the gates G1-G8 may be
selectively closed by a signal on a respective channel Ch1-Ch8 from
a decoder 82 to connect a signal placed a common bus line 84 from
the signal generator 60 to the speaker 42 in a respective one of
the transducer units 40A-40H. It may be understood that the signal
provided from the audio switch 62 may be amplified at the speakers
42 by an amplifier 42a associated with each of the speakers 42,
wherein the speaker 42 and amplifier 42a form a transmission module
43A-43H for a respective transducer unit 40A-40H.
The decoder 82 has first, second and third address bits A0, A1, A2
for selecting channel addresses associated with each of the gates
G1-G8, and an enable bit EN for enabling activation of the selected
channel Ch1-Ch8. In an operation of the audio switch 62 a digital
I/O interface 86 is activated by the turbine control system 78 to
select a channel on the address bits A0, A1, A2 and the enable bit
is enabled, i.e., switched from an "all off"=0 state to an "enable
on"=1 state. For example, if A0=0, A1=0, A2=0, EN=1, then the first
channel Ch1 is activated and the signal generator 60 is connected
to the transmission module 43A of the first transducer unit 40A; if
A0=0, A1=1, A2=0, EN=1, then the third channel Ch3 is activated and
the signal generator 60 is connected to the transmission module 43C
of the third transducer unit 40C; and if A0=1, A1=1, A2=1, EN=1,
then the eighth channel Ch8 is activated and the signal generator
60 is connected to the transmission module 43H of the eighth
transducer unit 40H.
The described audio switch 62 may be used to sequentially provide a
signal from the signal generator 60, with sharp on and off ramps,
to each of the transmission modules 43A-43H. Further, it may be
understood that the same encoded signal may be provided from the
signal generator 60 to each of the transmission modules
43A-43H.
FIG. 6 illustrates an alternative configuration for transmitting
signals via the transmission modules 43A-43H. In this
configuration, a separate signal generator 60A-60H may be provided
for transmitting a unique encoded signal to each of the
transmission modules 43A-43H. The audio switch 62 comprises a
plurality of gates G1-G8 that may be actuated simultaneously by a
single channel Ch1 activated through a decoder via a digital I/O
interface 86 that is activated by the turbine control system 78.
Each of the gates G1-G8 connects one of the signal generators
60A-60H to a corresponding one of the transmission modules 43A-43H.
Hence, a plurality of encoded signals, e.g., eight unique or
distinct encoded signals, may be transmitted simultaneously across
the flow path 17 to provide time-of-flight data across all of the
transducer units 40 at a single point in time.
Alternatively, the different gates G1-G8 of FIG. 6 may be triggered
separately to provide the signals from the different signal
generators 60A-60H to the transmission units 43A-43H at different
selected times. In this case, the decoder 82 may be activated in a
manner similar to that described with reference to FIG. 5, with
separate addresses providing activation to corresponding channels
for the gates G1-G8.
It may be understood that various aspects of the acoustic signals
described for implementing the invention contribute to signals that
have a sparse autocorrelation, and enabling identification of the
signals as being distinct from non-signal related acoustic sounds
or noise, and that various techniques for performing
autocorrelation, as well as cross-correlation between transducer
units 40, may be used in identifying a correspondence between
transmitted and received signals for obtaining time-of-flight
data.
Further, although the above description is presented with reference
to providing a temperature determination within a combustor section
14 of the engine, the principles of operation described herein may
be implemented in any region of the engine where it is desirable to
obtain the temperature of a gas.
While particular embodiments of the present invention have been
illustrated and described, it would be obvious to those skilled in
the art that various other changes and modifications can be made
without departing from the spirit and scope of the invention. It is
therefore intended to cover in the appended claims all such changes
and modifications that are within the scope of this invention.
* * * * *
References